Hey there,
Hope you already got your death wobble fixed, but I had a similar problem on my 98' Cherokee. It turned out to be a bent rim. I'm not sure what happened, I did nothing on my Jeep as far as upgrades or repairs. I had not been offroad for a while. It just seemed like the transition from winter to spring caused these strange symptoms. My symptoms were, when I hit a certain speed it was like riding in a Saturn 5 rocket. The front end would violently shake, I could feel it in the pedals, in the steering, it felt like you described, like the front axle was going to fall off. A buddy of mine helped me replace the u-joints, the shocks, rotate the tires. It just so happened that in one of the tire rotations I noticably felt the shaking move from the front to the rear. The tire looked ok, so I went and bought a used rim for $30.00, put it on and it fixed the problem. Even if you are unsure which rim it is, for just over $100.00 purchase used rims and see if the problem goes away. Good luck.